One type of adhesive that has come into widespread commercial use in the past years is the pressure sensitive adhesive type and various kinds of pressure sensitive adhesives are available and are in widespread commercial use. These adhesives remain in a fluid state indefinitely and provide very effective adhesion for many different types of paper or film products including labels. This fluidity of "alive" condition of the adhesive is desired in order that the adhesive will flow and achieve a bond to any substrate brought into association therewith. Since these adhesives are of this liquid or flowable nature, they have a high tendency to ooze out at the edge of laminates or stacks of paper or other products with which they are associated. Particularly, a lot of these paper adhesive products are converted after their initial processing into laminates so as to provide a desired label or other end product. The converting operations usually involve cutting the initial paper-adhesive laminate sheet to reduce its size and thus the initial sheets are subjected to guillotine cutting and/or die cutting in most converting operations.
Inasmuch as it is very desirable to avoid any edge ooze of the adhesive during storage or converting of the products, some appreciable safeguards have been set up to be followed when processing the laminate. Thus, the cutting blades must be kept very sharp and usually a silicone coating is applied onto the cutting blade. Furthermore, adhesive bleed or ooze normally can be overcome by beveling the leading and trailing edges of the sheets at a 45.degree. angle and then rubbing the edges with a cloth bag filled with powder, such as zinc stearate that fixes itself to any adhesive at the edge and renders it non-tacky. These converting cuts must normally be done at the lowest possible pressure and the maximum number of sheets that can be cut at one time usually is about 100. Hence, the converting and cutting of the pressure sensitive adhesive laminates is a difficult process and it is hard to maintain the end product in its most desirable, usuable condition.
Obviously, if adjacent sheets are sticking together by adhesive at the edges of a plurality of stacked sheets, such adjacent sheets would move at the same time to the printing press and result in unusable products and scrap material.
The general object of the present invention is to reduce and/or avoid problems with edge ooze of pressure sensitive adhesives in making up various types of paper laminates and in enabling the laminates to be converted by guillotine type cutting actions and equivalents as they are being cut to size for the end product, and to provide such action without any edge ooze being obtained and with a minimum scrap being generated in the printing operation.
Another object of the present invention is to provide a new and improved type of pressure sensitive adhesive composition that is characterized by the absence of edge oozing or edge flow-out of the adhesive curing processing or converting of papers having these pressure sensitive adhesives thereon.
Another object of the invention is to use special polysiloxanes, i.e. silicone chemicals as additives to pressure sensitive adhesives which silicone appear to adsorb or graft onto other ingredients of the adhesives or take other unknown actions so as to reduce the tendency of the adhesive containing such silicone to have edge oozing of the adhesive during guillotine cutting and similar operations.
Another object of the invention is to provide an improved pressure sensitive adhesive using substantially conventional chemicals therein and to obtain the unexpected result of reducing the edge oozing of the adhesive by the presence of special silicone materials in the adhesive.
The foregoing and other objects of the invention will be made more apparent as the specification proceeds.